Refractance window drying is an emerging technology that allows the development of new dried foods with an acceptable shelf life from products widely consumed in the world with high nutritional content and health benefits, such as Dairy products. The present study aimed to determine the effect of temperature and product thickness during Refractance window drying in a laboratory scale dryer on the physicochemical properties of whole bovine milk and commercial flavored yogurt, using an optimal design model. The drying temperature range was between 40°C and 80°C, while the evaluated thickness ranged from 1 to 3 mm. Energy consumption, pH, moisture, water activity, color, solubility, hygroscopicity, and protein denaturation were determined by the reconstitution of the powders obtained and employing techniques such as gravimetric method, color analysis, and FTIR. Based on the results obtained the drying temperatures and thicknesses studied did not affect the secondary structure of proteins; the optimal operational conditions were 64.7°C and 0.001 m for whole milk and 63.7°C and 0.001 m for yogurt. These findings suggest that Refractance window drying is a suitable technology for obtaining dried dairy products, particularly for viscous foods such as yogurt.
Keywords: Energy consumption; FTIR; Protein denaturation; physicochemical properties.
The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).